Apparatus for correcting distortion in moving pictures and similar projections.



H. ALLISON. APPARATUS FOR CORRECTING DISTORTION IN MOVING PICTURES AND SIMILAR PROJECTIONS.

. APPLICATION FILED DEC. 7. T915 1 ,259,7 1 1 Patented Mar. 19, 1918.

HARVEY ALLISON, OF NEW YORK, N. Y., ASSIGNOR, BY MESNE ASSIGNMENTS, TO THE COMMERCIAL RESEARCH COMPANY, 0!? LONG ISLAND CITY, NEW YORK, A CORPO- BATION OF NEW YORK.

APPARATUS FOR CORRECTING DISTORTION IN MOVING PICTURES AND SIMILAR PROJECTIONS.

Specification of Letters Patent. yatented M 19, 1915.

Application filed December 7, 1915. Serial No. 65,551.

To all whom it may concern:

Be it known that I, HARVEY ALLrsoN, a citizen of the United States, residing at New York city, in the county of New York and State of New York, have invented certain new and useful Improvements in Apparatus for Correcting Distortion in Moving Pictures and Similar Projections, of which the following is a specification.

This invention relates to apparatus for correcting distortion in moving pictures and similar projections; and it comprises a combination of reflectors disposed in the path of the light rays from a projection machine, one of such reflectors being adapted to correct distortion of the rays due to the differences in length of distance of travel to difierent parts of the screen from the lens of the projection machine and the other reflector being arranged to neutralize the astigmatism of the first reflector; and the invention further comprises a combination with a projection machine and a screen which is positioned with respect to such machine in such manner that one part thereof is at a greater distance from the lens of the machine than another part, of two companion reflectors arranged in the path of the light rays from the machine, one of said reflectors being adapted to produce astigmatism of the rays of light from the machine and to project the dispersed rays upon the second reflector, and the second reflector being arranged to distort the rays in an opposite direction from the distortion produced by the relative positions of the screen and the machine, and the said second reflector being also arranged to produce a reverse astigmatism which neutralizes the astigmatism produced by said first reflector; all as more fully hereinafter set forth and as claimed.

It is substantially the universal practic in motion picture theaters to place the projection machine in a balcony or gallery for the purpose of securing 'the largest possible floor space and seating capacity for the theater. When the ,projection machine is thus elevated it is necessary to point the light rays downwardly, sometimes as much as 35 to 40 degrees, in order to project the picture u on the screen which is usually placed su stantially level with the eye of the patrons in the orchestra. Under such circumstances the resultant picture is somewhat distorted since, as is well known, the s1ze of the picture that a lens projects depends upon the distance the screen is from the lens; and if inclined light rays are projected against a Vertical screen under condltions above ointed out, the lower portion of the screen eing farther away from the lens than the upper portion, will display the picture wider at the bottom than at the top. In some theaters this distortion is very not ceable, and it is always objectionable. Vanous means, most of which depend upon optical illusion, have been tried to overcome it, but with only partial success.

I have found that the distortion of the light rays due to the relative positions of the screen and the machine can be entirely corrected by means of a plurality of warpedor asymmetric reflectors placed in the path of the light between the projection machine and the screen. To correct the noted distortion it is only necessary to warp one reflector but such a warped reflector in turn produces astigmatism with the result that the light rays reflected from the warped reflector cannot be focused sharply in any plane. The distortion noted is corrected but another is produced in its lieu. I have however found that if a second reflector warped in an opposite direction from the first be used, the astigmatism in the first reflector is neutralized by the reverse astigmatism in the second, enabling the picture to be sharply focused while at the same time the distortion of the picture is corrected.

The second reflector not only neutralizes the astigmatism of the first reflector but to some extent diminishes the amount of correction of the latter. Ordinarily therefore the first reflector should be warped more than is necessary merely to correct the distortion resulting from the relative positions of the screen and the machine.

For clarity of description I shall hereinafter refer to the first reflector or warped mirror as the correction reflector and I shall refer to the second warped mirror or reflector as the astigmatic reflector.

In the accompanying drawings, the figures illustrate, more or less diagrammatically, the principles upon which this invenmirror necessarily results in r ndering tion depends and also a combination of machine, mirrors and screens embodying my invention.

Figure 1 is a diagrammatic view of the screen, mirrors and projection machine, the screen being shown at. a lower elevation than the projection machine;

Fig. 2 is a plan view of the correction reflector;

Figs. 3, 4 and 5 are sections along lines 3-3, ta and 5 5 of Fig. 2;

Fig. 6 is a plan view of the astigmatic reflector;

Figs. 7, 8 and 9 are sections along lines 7-7, 88 and 99 of Fig. 6;

Fig. 10 is a diagram showing the correct relative dimension of a picture on the screen; and

Fig. 11 is a diagram showing the distortion on the screen of the picture from the projection machine.

Referring to the drawings, reference numeral 1 indicates a screen upon which pictures are projected, and 2 indicates a projection machine at a higher elevation than the screen. As I shall hereinafter point out, my invention provides means for placing the machine to either side of the screen if desired. The machine is indicated diagrammatically, 3 being the lamp house, 4 the film, and 5 the lens. According to my invention when the machine is at a higher elevation than the screen I place the correction reflector 6 in substantially the side position as shown. This reflector is warped or curved as is indicated in Figs. 2 to 5 inclusive. That is to say, the top 7 is bent so as to be convex on the front side, the convexity gradually diminishing toward the bottom and the lower edge 8 being straight. The amount of warping, or the curvature of this reflector, is of course controlled by the dimensions of the theater chamber and the distance of the reflector from the screen and from the machine. The curvature in Figs. 2 to 5 inclusive is shown somewhat exaggerated over that which I usually employ, for clarity of presentation.

This reflector 6 will correct the distortion due to the relative positions of the screen and the machine but the warping of the it astigmatic so that it is impossible with the use of this one mirror or reflector to focus the picture in any one plane.

To overcome the astigmatism of reflector" 6, I further provide an astigmatic reflector or mirror 9 curved in an opposite direction to the curvature of correction reflector 6. The top 10 is bent so as to be concave on the front side, the concavity gradually diminishing toward the bottom or lower edge 11 which is straight.

The light rays from the lens 5 of the projection machine are thrown against the astigmatic reflector 9 and from thence they are reflected out of focus upon the oppositely curved reflector 6 and this reflector transmits the rays to the screen in proper focus and at the same time corrects the distortion which would ordinarily result because of the difference in distance of the lower and the upper part of the screen from the projectionmachine lens.

In one way of regarding this invention I first disperse light rays from the lens by means of an astigmatic reflector and then by means of a second astigmatic reflector correct the amount of dispersion, and at the same time by the second astigmatic reflector correct the distortion; or in another way I correct the distortion by means of a distortion reflector which at the same time is astigmatic, and then cure the astigmatism of this reflector by projecting the rays against it from another astigmatic reflector having reverse astigmatism. As has been pointed out the astigmatic reflector 9 to a certain extent diminishes the amount of correction produced by warped reflector or correction reflector 6; and for that reason the latter should be warped more than would be necessary if it alone were used. It could be used alone to cure the distortion, and in that event the astigmatic reflector 9 would be replaced by a straight reflector; but as stated, this would result in displaying the light rays upon the screen entirely out of focus.

In actual practice relatively small mirrors may be used. With the large mirror, only 9 inches square, I have been able to perfectly correct distortion of light rays at angles up to 35 degrees; and with slightly larger mirrors I have corrected distortions resulting from even greater angles. The astigmatic reflector being nearer the lens may be of smaller size than the correction reflector.

In Figs. 10 and 11 I have shown, diagrammatically, the results of projection according to the present invention and according to the usual method of projection where the rays come from a projector at a higher level upon a receiving screen at a lower level; upon a screen asymmetrically placed as regards the projecting device. As will be noted, in Fig. 11, which represents the usual results of projection, the diagrammatically shown picture is wider at the bottom than is the top whereas in the showing of Fig. 10, which represents diagrammatically a picture projected in the present manner, the bottom and top are of the same length and the sides are parallel.

, While I have shown the mirrors warped in one particular way, it is evident that they may be warped in many difl'erent ways to produce the same result and it is evident that more than two reflectors or mirrors may be used. It is also evident that my invention permits the projection machine to be placed in other positions than that shown. For instance, it may be placed to either side of the screen and substantially on the same level, in which event the warping mirrors would be curved to correspond.

What I claim is:-

1. The combination with a projection machine and a receiving, screen asymmetrically positioned with respect thereto, of a reflector adapted to correct the distortion resulting from the-relative positions of the ma- "chine and the 'screen and a second reflector adapted to .c'orrect the astigmatism of the first reflector.

2. The combination with a projection machine and a receiving screen asymmetrically positioned with respect thereto, of two companion reflectors arranged in a path from the light rays from the machine, one of said reflectors being arranged to correct the distortion of the light rays and the other of said reflectors to neutralize the resultant astigmatism of its companion.

3. The combination with a projection machine and a receiving screen asymmetrically positioned with respect thereto, of a correction reflector and an astigmatic reflector, the latter transmitting the rays from the lens to the machine to the former and the former transmitting the rays to the screen. and correcting the distortion due to the relative positions of the screen and the machine.

4. The combination with a projection machine and a receiving screen asymmetrically positioned with respect thereto, of a mirror warped in such manner as to correct the distortion resulting from the relative positions of the machine and the screen and a second mirror warped to correct the resulting astigmatism of the first mirror.

5. The combination with a projection machine and a receiving screen asymmetrically positioned with respect thereto, of an astigmatic reflector adapted to disperse the light rays to a predetermined extent and a second reflector adapted to refocus the light rays and to correct the distortion resulting from the relative positions of the machine and the screen.

6. The combination with a projection machine and a receiving screen asymmetrically positioned with respect thereto, of a correction reflector and an astigmatic reflector neutralizing the astigmatism of the first said reflector.

In testimony whereof, I aflix my signature hereto.

HARVEY ALLISON.

Witnesses G. A. WADLEY, FRANCES B. WADLEY. 

